Allyl alcohol is a valuable chemical intermediate. Allyl alcohol can be produced by acetoxylation of propylene, followed by hydrolysis of the resulting allyl acetate. Acetoxylation to produce allyl acetate can be performed by reacting propylene, acetic acid, and oxygen in the vapor phase in the presence of a palladium catalyst. The reaction mixture is typically separated into a vapor stream comprising propylene, oxygen, carbon dioxide, which is generally recycled to the acetoxylation reaction, and a liquid stream comprising allyl acetate, acetic acid, and water. However, the liquid stream tends to contain heavy impurities. One such impurity is allyl diacetate, also known as allylidene diacetate or 1,1-diacetoxy-2-propene. The heavy impurities, like allyl diacetate, can deactivate solid acid catalysts used in a subsequent step for hydrolyzing allyl acetate. A few publications have taught removing the allyl diacetate by decomposing it before the liquid stream is hydrolyzed. See, for example, Japanese Pat. Appl. Nos. 01-250338, 2-096548, 61-238745, and 53-071009. Also see co-pending application Ser. Nos. 12/322,650, filed Feb. 5, 2009 and 12/653,677, filed Dec. 17, 2009.
Co-pending application Ser. No. 12/322,650 describes a process for purifying an acetoxylation mixture containing allyl diacetate by contacting the mixture in a vapor phase with a solid acidic catalyst to convert the allyl diacetate to acrolein and removing the acrolein from the reaction product. Co-pending application Ser. No. 12/653,677 teaches a process for purifying allyl acetate by distilling an acetoxylation mixture at elevated pressure to remove propylene and generate a first bottoms mixture comprising allyl acetate, acetic acid, acrolein, allyl diacetate, and 3-acetoxypropionaldehyde. The first bottoms mixture is flash vaporized, and the resulting vapor is contacted with a solid acidic catalyst to decompose the allyl diacetate. The flashed product, which comprises allyl acetate, acetic acid, and acrolein, is distilled to remove acrolein and generate a second bottoms mixture comprising allyl acetate and acetic acid. The second bottoms mixture may be used to manufacture allyl alcohol.
There is a need in the industry to develop more economic processes wherein the heavy impurities such as allyl diacetate are removed by more efficient methods.